NEW YORK (Reuters Health) - Getting enough selenium in your diet could help protect you from cancer of the esophagus, a large new study suggests.

People with the highest levels of this antioxidant mineral were at the lowest risk of developing squamous cell carcinoma of the esophagus, Dr. Jessie Steevens of Maastricht University Medical Center in The Netherlands and her colleagues found.

The amount of selenium in the soil where food is grown determines its selenium content. There's some evidence for a link between selenium levels and stomach and esophageal cancer, and Steevens and colleagues say it's important to look at subtypes of these cancers separately because they are likely to have different causes.

The researchers looked at the relationship between selenium levels and three different types of cancer: esophageal squamous cell carcinoma (ESCC), which arises from the cells lining the upper esophagus; esophageal adenocarcinoma (EAC), which begins in gland cells located where the esophagus joins the stomach; and gastric cardia adenocarcinoma (GCA), which involves the upper part of the stomach.

"EAC and GCA are specifically of interest," the investigators wrote in the journal Gastroenterology, because the incidences of these cancers have risen in the US and Europe during the past decades.

The researchers looked at data from the Netherlands Cohort Study, which followed 120,852 men and women 55 to 69 years old for 16 years. They compared selenium levels in 64 patients who developed ESCC during follow-up; 112 EAC patients; 114 GCA patients; and 2,072 cancer-free controls. All had provided toenail clippings at the study's outset; the selenium content of a person's nails is considered to be an accurate measurement of their levels of the mineral over the previous year.

The higher a person's selenium levels, the researchers found, the lower their likelihood of developing ESCC. GCA also was associated with selenium levels, but the relationship was "borderline significant"; it was stronger for women than for men. Overall there was no relationship between selenium levels and EAC, but when the researchers looked separately at women and people who had never smoked, they did find an association between higher selenium levels and EAC risk. There was also a relationship between selenium intake and EAC risk in people with lower intakes of several antioxidant nutrients.

The findings, conclude the researchers, suggest that low selenium levels may increase risk of ESCC and GCA, as well as EAC in women, never-smokers, and people with low antioxidant intakes. They caution, however, that the findings need to be confirmed by other researchers.